Allergies Overview, Types, Causes, Novel Therapies

An allergen is a substance that triggers an allergic reaction in the body. When the body encounters an allergen, it produces an immune response known as an allergic reaction. Allergies are a type of immune response that occurs when the immune system overreacts to a harmless substance, mistaking it as a threat to the body.

The common types of allergies include:

  1. Food allergies
  2. Seasonal allergies (e.g. pollen, dust mites)
  3. Drug allergies
  4. Insect sting allergies
  5. Latex allergies

Certain diseases and conditions such as asthma, eczema, and hay fever can increase the likelihood of developing allergies. Genetics also play a role in developing allergies, and certain genes have been identified that increase the likelihood of developing allergies. Mutations in the filaggrin gene have been associated with an increased risk of developing eczema and asthma, which are both conditions associated with allergies.

Heredity also plays a role in developing allergies, as individuals with a family history of allergies are more likely to develop them themselves. Other factors that can increase the likelihood of developing allergies include exposure to pollution, smoking, and having a weakened immune system.

Viruses such as the common cold can cause allergies to worsen in some individuals. Seasonal allergies, also known as hay fever or allergic rhinitis, can cause symptoms such as sneezing, runny nose, itchy eyes, and congestion. Severe seasonal allergies can lead to symptoms such as difficulty breathing, wheezing, and chest tightness. Common allergy symptoms include hives, swelling, itching, and digestive problems such as nausea and diarrhea.

Certain viruses have been shown to contribute to the development of allergic diseases. Some of these viruses include:

  1. Respiratory syncytial virus (RSV): RSV is a common virus that causes respiratory infections in infants and young children. Studies have shown that RSV infections can increase the risk of developing asthma later in life.
  2. Rhinovirus: Rhinovirus is a common cause of the common cold. Studies have shown that children who are infected with rhinovirus are more likely to develop asthma later in life.
  3. Epstein-Barr virus (EBV): EBV is a virus that is associated with infectious mononucleosis. Studies have shown that people who are infected with EBV may have an increased risk of developing allergic diseases.
  4. Human herpesvirus 6 (HHV-6): HHV-6 is a virus that is associated with roseola, a common childhood illness. Studies have shown that HHV-6 infections may increase the risk of developing allergic diseases.
  5. Hepatitis A virus (HAV): HAV is a virus that can cause liver disease. Studies have shown that HAV infections may increase the risk of developing food allergies.

It is important to note that not all individuals who are infected with these viruses will develop allergic diseases, and that other factors such as genetics and environmental factors also play a role in the development of allergies.

There is still much research needed to fully understand the complex relationship between allergies and neurological systemic diseases like multiple sclerosis (MS) and autoimmune disorders like lupus. However, some studies have suggested that individuals with certain allergies may have a higher risk of developing these conditions.

One theory is that allergies may contribute to chronic inflammation in the body, which can then lead to autoimmune diseases. In the case of MS, it is thought that allergens may trigger an immune response that causes damage to the myelin sheath that surrounds and protects nerve cells in the brain and spinal cord.

Similarly, in the case of lupus, it is thought that certain environmental triggers, such as allergens, may contribute to the development of the condition in individuals who are genetically predisposed to it.

The genetic architecture of the human immune system is complex and involves many genes that control various aspects of the immune response. The immune system is made up of several different types of cells, each with its unique function. The genes that control the immune system are located throughout the human genome, and variations in these genes can affect how the immune system functions.

There are several types of genes that play a role in the immune system, including genes that control the production of immune cells, genes that regulate the activity of immune cells, and genes that encode proteins involved in the recognition and destruction of pathogens. Many of these genes are highly polymorphic, meaning that they have multiple variants that can affect immune function.

Variations in immune-related genes can impact an individual’s susceptibility to infectious diseases, autoimmune diseases, and allergies. For example, variations in the HLA (human leukocyte antigen) genes, which are involved in the recognition of foreign antigens, are associated with an increased risk of autoimmune diseases such as multiple sclerosis and lupus. Similarly, variations in genes involved in the production of immunoglobulin E (IgE), an antibody that is associated with allergies, can increase an individual’s risk of developing allergic diseases.

The intensity of allergic response to an allergen is primarily determined by the adaptive immune system, specifically by a type of immune cells called T-helper cells. T-helper cells produce cytokines, which are signaling molecules that can stimulate or suppress an immune response. In allergic reactions, a specific type of T-helper cell called Th2 cells produce cytokines that promote the production of immunoglobulin E (IgE) antibodies, which in turn activate mast cells and basophils to release histamine and other inflammatory molecules, leading to allergy symptoms. Therefore, the activity and function of Th2 cells play a critical role in determining the intensity of an allergic response.

Th2 cells are a subset of T-helper cells that play a crucial role in allergic reactions and defense against extracellular parasites. Several diseases, conditions, and factors have been shown to influence the levels of Th2 cells in the body, including:

  1. Allergic diseases: Allergic diseases such as asthma, allergic rhinitis, and atopic dermatitis are characterized by an increased production of Th2 cells and cytokines.
  2. Parasitic infections: Parasitic infections induce Th2 cell-mediated immune responses, which are essential for the clearance of the parasite.
  3. Environmental factors: Environmental factors such as pollution, smoking, and exposure to allergens can trigger an increase in Th2 cells.
  4. Genetics: Genetic factors also play a role in determining the levels of Th2 cells in the body. Certain genetic variations have been associated with an increased risk of allergic diseases.
  5. Hormonal factors: Hormonal factors such as estrogen have been shown to enhance the Th2 immune response, leading to an increased risk of allergic diseases.
  6. Nutritional factors: Nutritional factors such as vitamin D deficiency and a high-fat diet have been shown to increase the production of Th2 cells.

Overall, Th2 cell levels are influenced by a complex interplay of genetic, environmental, hormonal, and nutritional factors, which ultimately determine the susceptibility to allergic diseases and other Th2 cell-mediated conditions.

Phagocytosis and apoptosis are two important mechanisms that help to maintain a healthy immune system by removing damaged or infected cells.

Phagocytosis is the process by which certain immune cells, such as macrophages and neutrophils, engulf and digest foreign particles, including bacteria and dead cells. Factors that can affect phagocytosis include the presence of antibodies that can bind to the foreign particles and make them more recognizable to immune cells, as well as the overall health and function of the immune cells themselves.

Apoptosis, on the other hand, is a programmed cell death that occurs when a cell is no longer needed or has become damaged or infected. Factors that can affect apoptosis include changes in the cell’s environment, such as exposure to toxins or radiation, as well as genetic factors that control the cell’s ability to respond to these changes.

Other factors that can affect both phagocytosis and apoptosis include the overall health of the individual, including factors such as nutrition, exercise, and exposure to toxins or pollutants. Additionally, certain medications or medical conditions may affect these processes, either by enhancing or inhibiting their activity.

B cell immunity and T cell immunity are both important components of the adaptive immune system, but they differ in their mechanisms and functions.

B cells are responsible for producing antibodies, which are proteins that recognize and neutralize pathogens such as viruses and bacteria. When a pathogen enters the body, B cells are activated and start producing antibodies that specifically recognize the pathogen. These antibodies can then bind to the pathogen and prevent it from infecting cells. B cells also play a role in immunological memory, which allows the immune system to mount a more rapid and effective response to previously encountered pathogens.

T cells, on the other hand, recognize and destroy infected or abnormal cells. There are two main types of T cells: CD4+ T cells, also known as helper T cells, and CD8+ T cells, also known as cytotoxic T cells. Helper T cells coordinate the immune response by secreting cytokines that activate other immune cells, including B cells and cytotoxic T cells. Cytotoxic T cells directly kill infected or abnormal cells by releasing toxic molecules such as perforin and granzyme.

Overall, B cells are important for producing antibodies that neutralize pathogens, while T cells are important for destroying infected or abnormal cells. Both types of cells work together to mount an effective immune response.

Acquired immunity to a chronic viral infection involves the activation of T cells and B cells, which produce cytokines and antibodies to fight the viral infection. In some cases, the cytokines produced by T cells can also activate mast cells and basophils, which are involved in the allergic response. This can lead to the development of allergic diseases, such as asthma and allergic rhinitis, in individuals with chronic viral infections. The exact mechanisms underlying the link between chronic viral infections and allergic diseases are still being studied, but it is thought to involve a complex interplay between the immune system and various environmental factors.

Mast cells are a type of white blood cell that play a key role in the immune system’s response to certain allergens and pathogens. They are found throughout the body, particularly in the skin, respiratory tract, and digestive system, and contain granules filled with various chemicals, including histamine, cytokines, and proteases. When mast cells are activated by an allergen or pathogen, they release these chemicals into the surrounding tissues, leading to inflammation and the symptoms of an allergic reaction. Mast cells also play a role in wound healing and defending against parasitic infections.

The number and distribution of mast cells in the human body can vary between individuals and can be influenced by a variety of factors such as age, gender, and genetics, as well as environmental and lifestyle factors. Mast cell disorders and diseases that involve mast cells, such as mastocytosis and allergies, can also affect the number and function of mast cells in the body. However, these conditions are not associated with any specific human race.

Inherited genetic mutations can play a role in the development of mast cell disorders, which are conditions characterized by the abnormal accumulation and activation of mast cells in various organs and tissues. Mast cell disorders can be caused by genetic mutations that affect the regulation of mast cell growth and activity, including mutations in genes such as KIT, which encodes a protein that regulates mast cell proliferation and survival.

Furthermore, inherited genetic mutations and disease predispositions can also affect the likelihood of developing allergies, which can be triggered by the release of mast cell mediators in response to allergens. For example, mutations in genes involved in the regulation of the immune system, such as those associated with atopy (a genetic predisposition to develop allergies), can increase the risk of developing allergies and related conditions. Additionally, certain diseases that are associated with immune dysfunction or inflammation, such as autoimmune diseases and chronic infections, may also increase the risk of developing mast cell disorders and related allergic conditions.

Here are some of the top 10 drugs that can cause allergies:

  1. Penicillin and related antibiotics (e.g. amoxicillin, ampicillin)
  2. Sulfonamides (e.g. sulfamethoxazole, trimethoprim-sulfamethoxazole)
  3. Nonsteroidal anti-inflammatory drugs (NSAIDs) (e.g. aspirin, ibuprofen)
  4. Chemotherapy drugs (e.g. cisplatin, carboplatin)
  5. Anticonvulsants (e.g. phenytoin, carbamazepine)
  6. Radiographic contrast media (e.g. iodine-based contrast agents)
  7. Insulin
  8. Monoclonal antibodies (e.g. rituximab, trastuzumab)
  9. Vaccines (e.g. influenza vaccine, measles-mumps-rubella vaccine)
  10. Local anesthetics (e.g. lidocaine, bupivacaine)

It is important to note that any medication has the potential to cause an allergic reaction, and that these reactions can vary in severity. If you are concerned about an allergic reaction to a medication, it is important to talk to your healthcare provider.

The top 10 food allergies are:

  1. Peanuts
  2. Tree nuts (such as almonds, cashews, and walnuts)
  3. Shellfish (such as crab, lobster, and shrimp)
  4. Fish
  5. Milk
  6. Eggs
  7. Soy
  8. Wheat
  9. Sesame
  10. Mustard

The causes of food allergies are not fully understood, but they are believed to be caused by a combination of genetic and environmental factors. Some people may be more predisposed to developing food allergies due to their genetics, while others may develop them as a result of environmental factors such as exposure to certain allergens.

Certain ethnic groups are more likely to have certain food allergies. For example, peanut allergies are more common among people of African, Asian, and Hispanic descent, while milk and wheat allergies are more common among people of European descent.

Food allergies are also more common in developed countries, particularly in Western countries such as the United States, Canada, and Europe. This may be due to factors such as changes in diet and lifestyle, increased exposure to environmental allergens, and improved hygiene.

To suspect an allergic reaction, one should be aware of the signs and symptoms of an allergic reaction, which can include:

  1. Skin rash or hives
  2. Itching or swelling, especially of the face, lips, or tongue
  3. Difficulty breathing or shortness of breath
  4. Wheezing or coughing
  5. Rapid or weak pulse
  6. Nausea or vomiting
  7. Dizziness or fainting
  8. Loss of consciousness

The difference between systemic diseases like status asthmaticus or COPD episodes and common allergies is that systemic diseases are chronic conditions that affect the respiratory system, while allergies are acute reactions to specific allergens that can affect multiple systems in the body.

If an allergic reaction is left untreated, it can progress and become more severe, potentially leading to anaphylaxis, which is a life-threatening reaction. Anaphylaxis can cause a sudden drop in blood pressure, difficulty breathing, and loss of consciousness, and it requires immediate emergency medical attention.

Some allergic reactions are considered life-threatening and emergencies because they can progress quickly and become severe, leading to anaphylaxis. People who have previously experienced an anaphylactic reaction are at higher risk of experiencing another one.

The time it takes to go from anaphylaxis to a life-threatening shock can vary depending on the individual and the severity of the reaction. In some cases, the onset of anaphylaxis can be rapid and progress to life-threatening shock within a matter of minutes. In other cases, the symptoms may develop more slowly and the individual may have some time before the reaction becomes severe. However, it’s important to note that anaphylaxis is a medical emergency and requires prompt treatment to prevent the reaction from progressing to shock. If you suspect that you or someone else is experiencing anaphylaxis, seek immediate medical attention.

People who are more likely to develop an acute severe life-threatening reaction to a bee sting are those who have a history of severe allergic reactions, including anaphylaxis, to bee stings. This can be determined through allergy testing.

The toxic effect of venom from bees is caused by a complex mixture of chemicals, including enzymes, peptides, and proteins. The venom can cause local tissue damage and pain at the site of the sting, as well as systemic effects such as nausea, vomiting, and sweating. The venom can also affect the cardiovascular and respiratory systems, leading to anaphylaxis in some people.

There are several novel therapies being researched and developed for allergies. Here are some examples:

  1. Biologics: Biologic drugs, also known as monoclonal antibodies, target specific cells and proteins involved in the allergic response. For example, omalizumab is a biologic drug approved for the treatment of severe asthma and chronic idiopathic urticaria.
  2. Gene therapy: Gene therapy is a promising area of research for the treatment of allergies. It involves inserting or modifying genes to produce a therapeutic effect. For example, researchers are exploring the use of gene therapy to target immune cells involved in the allergic response.
  3. Allergen immunotherapy: Allergen immunotherapy, also known as allergy shots, involves exposing the body to small amounts of an allergen over time to build up tolerance. Researchers are exploring new forms of immunotherapy, such as sublingual immunotherapy (SLIT) and epicutaneous immunotherapy (EPIT).
  4. Nanoparticle-based therapies: Nanoparticles are small particles that can be engineered to carry drugs or other molecules to specific cells or tissues in the body. Researchers are exploring the use of nanoparticle-based therapies for the treatment of allergies.
  5. Microbial-based therapies: The gut microbiome, which is the collection of microorganisms in the human digestive tract, plays a role in immune function and may influence the development of allergies. Researchers are exploring the use of microbial-based therapies, such as probiotics and fecal microbiota transplantation, for the treatment of allergies.

It’s important to note that these therapies are still in the early stages of development and may not be widely available for some time. Patients should always consult with their healthcare provider for the most appropriate treatment options for their allergies.


Verified by: Rami Diab (May 7, 2023)

Citation: Rami Diab. (May 7, 2023). Allergies Overview, Types, Causes, Novel Therapies. Medcoi Journal of Medicine, 7(2). urn:medcoi:article22288.

, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

There are no comments yet

× You need to log in to enter the discussion
© 2024 Medcoi LLC, all rights reserved.
go to top